Optimization Of Coalbed Methane Drainage System

As the rapid development of economy in China and the condition of the shortage of oil and gas energy, Chinese requirement for the exploitation of CBM is growing. The gas content of coal seams is foundation, the permeability of coal seams is the key and reasonable producing measure is the guarantee of exploiting CBM efficiently. Based on the summary of domestic and foreign scholars’research on the change regulation of permeability of coal seams in different during production and the CBM well drainage low, this paper established a prediction model of permeability of CBM well after hydraulic fracturing with theories of CBM geology and exploitation, which adapt to most domestic CBM wells with low permeability and low pressure. It also divided the drainage and production phase of most CBM vertical wells after hydraulic fracturing into six stages:saturated water uniflow, unsaturated water uniflow, gas-water two-phase flow constant pressure gas-water two-phase flow only in certain direction transfer and constant pressure. Combined with the geologic parameter and reservoir stimulation parameter, this paper contracted the six stages by the dynamic change of permeability of coal seams during drainage and production phase. This paper numerically analyzed the change of engineering parameters including water production rate, gas production rate, dynamic liquid level height, bottom-hole pressure, desorption radius and pressure propagation radius caused by the change of downhole pressure in different drainage and production phases and wrote a software to optimize drainage and production system of coal gas well and theoretically refine the drainage and production system. Meanwhile, Based on the analysis of geology, core, well test data and hydraulic fracturing data of well Y1, the software for optimization of drainage and production system of coal well used in well Y1to establish reasonable drainage and production system. Analyzing the factors than influence the drainage and production system of coal well with the data obtained from simulation so that we can understand the drainage and production system of coal well deeply.